63 research outputs found

    Epitaxial growth of FeSe0.5_{0.5}Te0.5_{0.5} thin films on CaF2_2 substrates with high critical current density

    Full text link
    In-situ epitaxial growth of FeSe0.5_{0.5}Te0.5_{0.5} thin films is demonstrated on a non-oxide substrate CaF2_2. Structural analysis reveals that compressive stress is moderately added to 36-nm thick FeSe0.5_{0.5}Te0.5_{0.5}, which pushes up the critical temperature above 15 K, showing higher values than that of bulk crystals. Critical current density at TT = 4.5 K reaches 5.9 x 104^4 Acm2^{-2} at μ0H\mu_0H = 10 T, and 4.2 x 104^4 Acm2^{-2} at μ0H\mu_0H = 14 T. These results indicate that fluoride substrates have high potential for the growth of iron-based superconductors in comparison with popular oxide substrates.Comment: 9 pages, 3 figures, to be published in Applied Physics Express 4, 053101 (2011

    Binary Formation with Different Metallicities: Dependence on Initial Conditions

    Full text link
    The fragmentation process in collapsing clouds with various metallicities is studied using three-dimensional nested-grid hydrodynamics. Initial clouds are specified by three parameters: cloud metallicity, initial rotation energy and initial cloud shape. For different combinations of these parameters, we calculate 480 models in total and study cloud evolution, fragmentation conditions, orbital separation and binary frequency. For the cloud to fragment during collapse, the initial angular momentum must be higher than a threshold value, which decreases with decreasing metallicity. Although the exact fragmentation conditions depend also on the initial cloud shape, this dependence is only modest. Our results indicate a higher binary frequency in lower-metallicity gas. In particular, with the same median rotation parameter as in the solar neighbourhood, a majority of stars are born as members of binary/multiple systems for < 10^-4 Z_sun. With initial mass < 0.1 M_sun, if fragments are ejected in embryo from the host clouds by multi-body interaction, they evolve to substellar-mass objects. This provides a formation channel for low-mass stars in zero- or low-metallicity environments.Comment: Accepted for publication in MNRAS. High resolution figures are available at http://www2-tap.scphys.kyoto-u.ac.jp/~machidam/astro-ph/metallicity.pd

    Activity-Guided Fractionation of Green Tea Extract with Antiproliferative Activity against Human Stomach Cancer Cells

    Get PDF
    Epidemiological studies have suggested that the consumption of green tea provides protection against stomach cancer. Fractionation of green tea extract, guided by antiproliferative activity against human stomach cancer (MK-1) cells, has resulted in the isolation of six active flavan-3-ols, epicatechin (EC), epigallocatechin (EGC), epigallocatechin gallate (EGCg), gallocatechin (GC), epicatechin gallate (ECg), gallocatechin gallate (GCg), together with inactive glycosides of kaempferol and quercetin. Among the six active flavan-3-ols, EGCg and GCg showed the highest activity, EGC, GC, ECg followed next, and the activity of EC was lowest. These data suggest that the presence of the three adjacent hydroxyl groups (pyrogallol or galloyl group) in the molecule would be a key factor for enhancing the activity. Since reactive oxygen species play an important role in cell death induction, radical scavenging activity was evaluated using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical. The order of scavenging activity was ECg?EGCg?EGC?GC?EC. The compounds having a galloyl moiety showed more potent activity. The contribution of the pyrogallol moiety in the B-ring to the scavenging activity seemed to be less than that of the galloyl moiety
    corecore